بسم الله الرحمن الرحيم

1. بسم الله الرحمن الرحيم

2. Haemophilusinfluenzae Diseases • Sinusitis, otitis media & pneumonia are common. • Epiglottitis is uncommon. • H. influenzae used to be a leading cause of meningitis, but vaccine has greatly reduced number of cases.

3. Haemophilusinfluenzae Characteristics • Small gram-negative (coccobacillary) rods. • Requires factors X (hemin) & V (NAD) for growth. • Of six capsular polysaccharide types, type b causes 95% of invasive disease. • Type b capsule is polyribitol phosphate. Habitat and Transmission • Habitat is the upper respiratory tract. • Transmission is via respiratory droplets.

4. Haemophilusinfluenzae Pathogenesis • Polysaccharide capsule is the most important determinant of virulence. • Unencapsulated ("untypeable") strains cause mucosal infections but not invasive infections. • IgA protease is produced. • Most cases of meningitis occur in children younger than 2 years of age, because maternal antibody has waned & immune response of child to capsular polysaccharides can be inadequate.

5. Haemophilusinfluenzae Laboratory Diagnosis • Gram-stained smear plus culture on chocolate agar. • Growth requires both factors X & V. • Determine serotype by using antiserum in various tests, e.g., latex agglutination. • Capsular antigen can be detected in serum or cerebrospinal fluid.

6. Haemophilusinfluenzae Treatment • Ceftriaxone is the treatment of choice for meningitis. • Approximately 25% of strains produce β  -lactamase. Prevention • Vaccine containing type b capsular polysaccharide conjugated to diphtheria toxoid or other protein is given between 2 & 18 months of age. • Rifampin can prevent meningitis in close contacts.

7. Bordetella pertussis Diseases Whooping cough (pertussis). Characteristics Small gram-negative rods. Habitat and Transmission • Habitat is the human respiratory tract. • Transmission is via respiratory droplets.

8. Bordetella pertussis Pathogenesis • Pertussis toxinstimulates adenylate cyclase by adding ADP-ribose onto inhibitory G protein. • Toxin has two components: • - Subunit A: has ADP-ribosylating activity • - Subunit B:binds toxin to cell surface receptors. • Pertussis toxin causes lymphocytosis in blood by inhibiting chemokine receptors prevents lymphocytes from entering tissue, resulting in large numbers being retained in blood.

9. Bordetella pertussis Pathogenesis • Inhibition of chemokine receptors occurs because pertussis toxin ADP-ribosylates inhibitory G protein prevents signal transduction within cell • Extracellular adenylate cyclase is produced • inhibit killing by phagocytes. • Tracheal cytotoxin damages ciliated epithelium of respiratory tract.

10. Bordetella pertussis • Whooping cough is acute tracheobronchitis that begins with mild upper respiratory tract symptoms followed by severe paroxysmal cough, which lasts from 1 to 4 weeks. • Paroxysmal pattern is characterized by series of hacking coughs, accompanied by production of copious amounts of mucus, that end with inspiratory "whoop" as air rushes past narrowed glottis. • In adults, B. pertussis infection often manifests as paroxysmal cough of varying severity lasting weeks. The characteristic whoop is often absent. Adults with a cough lasting several weeks (often called the 100-day cough) should be evaluated for infection with B. pertussis.

11. Bordetella pertussis Laboratory Diagnosis • Gram-stained smear plus culture on Bordet-Gengou agar. • Identified by biochemical reactions & slide agglutination with known antisera. • PCR tests are both sensitive & specific. Colonies of Bordetella pertussis growing on Bordet-Gengou agarThis fastidious bacterium grows as small colonies with a pearl-like sheen on this medium.

12. Bordetella pertussis Treatment Erythromycin. Prevention • Acellular vaccine containing pertussis toxoid & four purified proteins (recommended). • Killed vaccine: contains whole organisms. • Given to children in combination with diphtheria & tetanus toxoids (DTaP).

13. Legionella pneumophila Diseases Legionnaires' disease ("atypical" pneumonia). • Clinical picture vary from mild influenzalike illness to severe pneumonia accompanied by mental confusion, nonbloody diarrhea, proteinuria & microscopic hematuria. • Cough with scanty & nonpurulent sputum. • Most cases resolve spontaneously in 7 to 10 days, but in older or immunocompromised patients, infection can be fatal. • Pontiac fever is mild, flulike form of Legionella infection that does not result in pneumonia.

14. Legionella pneumophila Characteristics • Gram-negative rods (stain poorly with standard Gram stain) • Require iron & cysteine for growth in culture. Habitat and Transmission • Habitat is environmental water sources. • Transmission is via aerosol from the water source. • Person-to-person transmission does not occur.

15. Legionella pneumophila Pathogenesis • It has endotoxin. • Predisposing factors include: • - Older than 55 years of age • - Smoking damages alveolar macrophages • - High alcohol intake. • -Immunosuppressed patients (renal transplant recipients) • Organism replicates intracellularly, so cell-mediated immunity is important host defense.

16. Legionella pneumophila

17. Legionella pneumophila Laboratory Diagnosis • Microscopy with silver impregnation stain or fluorescent antibody. • Culture on charcoal yeast extract agar containing increased amounts of iron & cysteine. • Urinary antigen provides rapid diagnosis. • Serologically by detecting rise in antibody titer in patient's serum. • Hyponatremia (serum sodium ≤ 130 mEq/L) is important laboratory finding that occurs more often in Legionella pneumonia than in pneumonia caused by other bacteria.

18. Legionella pneumophila H & E stained lung sections of patient from whom legionella pneumophila was isolated stained with CDC's modification of Dieterle silver impregnation procedure. small, blunt pleomorphic intracellular & extracellular bacilli which stain brown to black against a pale yellow background (500X) Legionella pneumophila growing on GVPC agar Charcoal yeast extract agar

19. Legionella pneumophila Treatment • Azithromycin or erythromycin. • Rifampin can be added in severe cases. Prevention No vaccine or prophylactic drug is available.